According to her, at 6 a.m. Thursday, the Chinese fishing boat marked 62226, assisted by two Chinese "fishery administration" vessels marked 311 and 303, "intentionally rammed" into the survey cables of Viking II, a Norwegian ship chartered by the Vietnam National Oil and Gas Group (PetroVietnam).

Viking II was conducting a seismic survey well inside the 200 nautical mile exclusive economic zone of Vietnam at that time and had let off flare to warn off the Chinese boats, Nga said.

The incident was "premeditated and carefully calculated" as China aims to bring an undisputed area into the territorial row, Nga told reporters.

"This is unacceptable to Vietnam," she said, adding that the foreign ministry had met Chinese embassy officials Thursday afternoon "to express our opposition to such acts".

According to the Vietnamese spokeswoman, the Chinese boat 62226 trailed a cable-cutting device into the vicinity of Viking II and became trapped in the network of underwater cables in use by the Vietnamese vessel. As a result, the ship Viking II could not operate normally.

The two Chinese fishing enforcement vessels and other fishing boats arrived to assist the Chinese boat, Nga said.

"China's systematic acts were aimed at "¦ carrying out its ambition to make China's nine-dash line claim a reality."

Nguyen Phuong Nga,Vietnamese foreign ministry spokesperson

She said the area in question is completely under Vietnamese sovereignty according to the 1982 United Nations Convention on the Law of the Sea.

The Chinese boat "seriously violated Vietnam's sovereignty and jurisdictional rights, "¦ and go against the common perception of senior leaders of the two countries on maintaining peace and stability in the East Sea, while causing significant economic losses [for PetroVietnam]."

The incident took place just two weeks after a Chinese "marine surveillance" vessel on May 26 cut the exploration cables of the Binh Minh 02, another Vietnamese oil survey ship in Vietnam's continental shelf. It caused "continuous tension" to the East Sea (South China Sea) situation, Nga said.

"China's systematic acts were aimed at "¦ carrying out its ambition to make China's nine-dash line claim a reality," Nga said, referring to China's claim of a vast U-shape over most of the East Sea's 648,000 square miles (1.7 million square km), including the Spratly (Truong Sa) and Paracel (Hoang Sa) archipelagos.

In a speech to mark the Vietnamese Week of Sea and Islands on Wednesday, Prime Minister Nguyen Tan Dung reaffirmed "the incontestable maritime sovereignty of Vietnam towards the two archipelagos, the Hoang Sa and Truong Sa", which the people and army have "the strongest determination" to protect.